As a method of measuring the positions or positional errors of several shot areas on a semiconductor wafer in a step-and-repeat exposure apparatus, i.e., a so-called stepper for semiconductor manufacturing, determining the shot order of the respective shot areas on the wafer in accordance with the measurement result, and sequentially aligning the respective shot areas on the wafer to the reticle position on the basis of the determined shot order, a technique disclosed in, e.g., Japanese Patent Laid-Open No. 63-232321 already filed by the present applicant is known. For more accurate alignment, methods of evaluating an alignment waveform using its contrast or symmetry and selecting an alignment detection means on the basis of the evaluation result are disclosed in Japanese Patent Laid-Open Nos. 5-335212 and 4-3413 already filed by the present applicant.
Generally, a semiconductor element is formed by a plurality of processes. For this reason, the optical characteristic of an alignment mark changes for each process depending on the wafer underlying substance, alignment mark step, or a change in covering or film thickness of a photosensitive material (resist). In a conventional alignment method, a plurality of alignment means are prepared to cope with such changes. The alignment means are appropriately selected, and process parameters for alignment mark detection are fixed or manually input to cope with the changes. Selecting the alignment means or alignment parameters is very time-consuming. In addition, optimum alignment means or alignment parameters are not always selected.
Even when an alignment method is automatically selected, and an alignment waveform is evaluated, as in the above prior art, the apparatus must have a plurality of detection means in advance to do accurate alignment. This increases the apparatus cost, complicates the apparatus maintenance, and generates an offset due to an error factor that changes depending on the detection means. For these reasons, this method is not an all-round method for accurate detection.